There are several methods for recovering viscous oil and bitumen from underground heavy oil deposits. One such method is known as Steam Assisted Gravity Drainage (SAGD). During the SAGD process a pair of coextensive horizontal wells, spaced one above the other, are drilled close to the base of a viscous oil or bitumen deposit. The span of the formation between the wells is heated by thermal conductance using the circulation of steam through each of the wells to mobilize the bitumen located therebetween.
Once the bitumen is sufficiently heated the oil may be displaced or driven from one well to the other. This fluid communication is achieved by injecting steam through the steam injection well (usually the upper well) at less than fracture pressure, and opening the production well (usually the lower well), so that it can collect the draining liquid. The injected steam forms a steam chamber in the formation which continues to heat the formation, reducing the viscosity of the oil and increasing its mobility. This increase in mobility allows the heated oil to drain downwardly, through the force of gravity, towards the production well.
A steam generator located at the surface of the steam injection well generates and injects steam down a steam tubular. The steam is released from the steam tubular through exit ports and flows into the steam injection wellbore and then moves outward into the formation. The steam tubular may have several steam splitters, which distributes the steam in predetermined sections in the well. Typically, a steam splitter can be opened and closed based on the steam requirements during the SAGD operation.
In prior devices, the steam released from the steam tubular is unevenly dispersed at the exit ports or flows directly outward (radially) from the body of the steam tubular. This can result in the steam damaging and eroding the wellbore or damaging and creating holes in the liner of the steam injection wellbore.
The steam splitter described in Canadian Patent Number 2,765,812 has a shroud that surrounds the exit ports and the tubular and unevenly funnels the steam over the front and back of the tool, potentially causing damage to the wellbore. The use of a shroud results in uneven, uncontrolled distribution of steam. The steam from each exit port is grouped, forced to exit at common exits of the shroud, and is sent out in an untargeted, unpredictable manner.
Some known steam splitters only provide open and closed exit port positions and they do not allow an operator to customize the size or position of the holes or exit ports through which the steam escapes into the steam injection wellbore. Further, some steam splitters direct the flow of steam through the tool in such a manner that it may shorten the life of the tool itself. For example, the flow of steam in the tool described by Canadian Patent Number 2,765,812 travels through a shifting sleeve. This can cause damage to the shifting sleeve through erosion and reduce the lifespan of the tool.
Improved dispersion of steam is desirable to overcome the limitations in the known devices and to reduce potential erosion of both the tool and the steam injection wellbore.